22 February 2006 High-Power Al-free active region (λ = 852nm) laser diodes for atomic clocks and interferometry applications
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Atomic clocks will be used in the future European positioning system Galileo. Among them, the optically pumped clocks provide a more accurate alternative. For these systems, diode lasers emitting at 852nm are strategic components. The laser in a conventional bench for atomic clocks presents disadvantages for spatial applications. A better approach would be to realise a system based on a distributed-feedback laser. Thus we have developed laser structures emitting at λ=852nm, using an aluminium free active region. The device is a separate confinement heterostructure with a GaInP large optical cavity and a single compressive-strained GaInAsP quantum well. The broad-area laser diodes are characterised by low internal losses (<3 cm-1), a high internal efficiency (94%) and a low transparency current density (100A/cm2). For an AR/HR coated 2mm long around 4μm wide ridge diode, we obtain a low threshold current (40mA) and a high slope efficiency (0.90W/A). We obtain 852nm wavelength at 145mW (I=200mA, 15°C). We measure an optical power of 230mW (I=280mA) in a single spatial mode with the beam quality parameter M2=1.3. From our first attempt for a DFB laser, we obtained a threshold at 20°C of 45mA and a slope efficiency about 0.45W/A with an uncoated 2mm long around 4μm wide device. At 40mW (I=140mA,), both near and far fields in the slow axis are gaussian-shaped with respective full widths at 1/e2 of 7μm and 10.4°, corresponding to a single spatial mode emission with the beam quality parameter M2=1.2. At this power, the laser wavelength is 853.8nm with a side-modesuppression ratio over 30dB.
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V. Ligeret, F.-J. Vermersch, S. Bansropun, M. Lecomte, M. Calligaro, O. Parillaud, M. Krakowski, "High-Power Al-free active region (λ = 852nm) laser diodes for atomic clocks and interferometry applications", Proc. SPIE 6133, Novel In-Plane Semiconductor Lasers V, 613318 (22 February 2006); doi: 10.1117/12.644547; https://doi.org/10.1117/12.644547


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